Lecture 28: Connective tissue

Question 1

Components of Connective tissue

Answer 1

1) Cells (transient and permanent)
2) Extracellular matrix (ECM) = fibers, ground substance

• Supplied by blood, lymphatic vessels and nerves
• Alter these three components to make different types of connective tissue

Question 2

Why is connective tissue important

Answer 2

1) Supports (forms the stroma of the organs)
2) Repairs
3) Defense (immune function)
4) Nutrition (storage and transport)

Question 3

Embryonic connective tissue

Answer 3

1) Mesenchymal Connective tissue
-Contains mesenchymal cells, stem cells, tapered spindle appearance
-Sparsely arranged reticular fibers (Round)
-Abundant ground substance (GAG’s)
Function: Gives rise to other connective tissues

2) Mucous Connective tissue
- Contains mesenchymal cells, ground substance = MORE, Hyaluronan, gelatinous consistency to the matrix)
- Umbilical chord
- Provides fetus with protection and blood
- FIbers = star shaped

Question 4

Loose Connective tissue

Answer 4

1) Cell > fibers

2) Rich blood supply: allows oxy and co2 exchange, diffusion of hormones and growth factors
(Blood vessels can move easier through loose connective tissue bc less fibers, fibers = immovable)
-Epithelium needs blood supply, so under it will always be loose connective tissue

3) Location: Beneath epithelia linings, lamina propria, around grandular epithelium

Question 5

Dense Irregular Connective tissue

Answer 5

1) Fibers > Cells (than loose tissue)
2) No orientation of collagen fibers (resistance to stress in all directions
3) Organs capsules, periosteum, dermis

Question 6

Dense regular Connective tissue

Answer 6

1) Specific (regular) orientation of collagen fibers
2) Tensile strength

Components

1) Fibroblasts = tendon: tendinocytes
2) Collagen fibers (type 1) = gives strength

Question 7

Structure of tendon

Answer 7

1) Epitendineum: Covers entire tendon
2) Peritendineum: Covering around a group of fascicles
3) Endotendineum: Connective tissue covering around a group of fibers

Question 8

Elastic tissue

Answer 8

1) Elastic fibers:
- Core of elastin + fibrillin microfibrils
- REQUIRES ORECEIN, RESOCIN, OR VERHOEFF’S staining
- Connected to desmosine and isodesmosine
- USED for stretch

2) Ligamentum flavum, vocal ligament, suspensory ligament of the penis

Question 9

White Adipose Connective tissue

Answer 9

• Cells = large
• Nucleus = peripheral
• Lipid droplet= one
• Pale staining = negative profiling
• Functions = fat storage

Question 10

Brown Adipose Connective tissue

Answer 10

• Cells = smaller than white
• Nucelus= central
• Lipid droplets= many
• Function= Energy release

Question 11

What are the types of specialized connective tissue?

Answer 11

1) Cartilage
2) Bone
3) Blood

Question 12

Ehlers-Danlos Syndrome

Answer 12

-Abnormal collagen productions bc of mutation in genes encoding the alpha-chains in various collagens (Enzyme deficiency)

-Effects Collagen Type III or Type V
Symptoms Type III:
-Def Col3A1 gene
1) Fragile skin and vascular cell walls
2)  Early morbidity and mortality (bc vessels and organs rupture)

Symptoms Type V:

• Def Col5A1 and COl5A2
  1) Hyper mobility of joints/digits
  2) Hyperextensible skin

Question 13

Marfan’s Syndrome

Answer 13

-Decreased elastic fibrillin (Fibrillin gene)

Symtoms:

1) Tall stature
2) Long limbs, fingers, toes

-Cardiovascular manifestations = aortic aneurysm and mitral valve prolapse

Question 14

Fibrosis, keloids

Answer 14

Due to increased collagen

• Hypertrophic scar = Scars when more raids than normals, but within original wound boundary
• Keloid scar = Extending into surrounding tissue

Question 15

Scurvy

Answer 15

Decreased collagen (vitamin C) = decreased stability and strength of collagen

Symptoms:
-Bleeding gums, hemorrhages, poor wound healing

Question 16

Anaphylactic shock

Answer 16

Increased mast cell release of histamine

Question 17

Edema

Answer 17

Swelling due to increased tissue fluid

Question 18

Collagen Fibers

Elastic Fibers

Reticular fibers

Answer 18

Collagen Fibers:
-Thicker, Do not branch, intersect

Elastic Fibers:
-Thinner, do not branch, intersect (allow strength)

Reticular Fibers:

• Type III Collagen
• Function: Filters blood, allows large volume changes while maintaining structural integrity
• Found: (Liver, spleen)
• Short, thin, highly BRANCHING
• Components:
  1) Fibroblasts
  2) Argyrophilic reticular fibers

Function:

1) Supports myeloid and lymphoid organs (Bone marrow, lymph nodes, spleen)
2) Liver
3) Endocrine tissue
4) Nerve tissue

Question 19

Hydroxy proline

Hydroxy lysine

Answer 19

Hydroxy proline
-Gives more Hydrogen bonding = more tight winding triple helix

Hydroxyl lysine
-Useful bc has OH, can add a sugar = O-linked-glycosylation

-Both involved in hydroxylation, need Vit C to work

Question 20

Osteogenesis Imperfecta (OI)

Answer 20

• Brittle bones disease (Autosomal dominant)
• Mutation in COL1A1 and COL1A2= def in collagen
• Displacement of glycine in bone collagen = improper formation and stability of collagen triple-helix

Types:

1) OI Type I: Osteogenesis Imperfecta Tarda
- Mildest form
- Long bone fractures in early childhood
- Hearing loss
- Blue sclera

2) OI Type II: Osteogenesis Imperfecta Congenita
- Death in utero due to respiratory problems
- Underdeveloped lungs
- Fragile rib cage

3/4) OI Type III and IV:

• Severe scoliosis
• Bone malformations
• Dentiogenesis imperfecta –> discolored/weak teeth

Question 21

Elastin

Answer 21

Similarities to collagen:

• Contains glycine, lysine, proline
• Secreted as tropoelastin
• Some hydroxyproline (less tho)

Differences from collagen:

1) No hydrozylysine
2) Not glycosylated

-Assembled into elastin fibers w crosslinking

Question 22

Fibrillin

Answer 22

• Made of elastin and microfibrils
• Deficiency = Marfans syndrome (Mutation FBN1-gene)

Symp Marfans:

• aortic aneurysms
• Tall/long bodies/fingers
• Sunken chest
• lens issues